The automobile industry is constantly striving to use space-saving and acoustically effective trims so as to be able not only to increase comfort in the passenger compartment, but also to reduce the noise level in the passenger compartment and the emission of noise to the outside. In particular, there is considerable interest in measures for the effective reduction of the noise pollution inside the vehicle caused inter alia by engine, exhaust or tyre noise.
Thus, for example, an adhesive insulation system is known from EP-A 0 253 376, in which a first covering is applied to the substrate, which covering carries a multi-ply insulating layer acting as an acoustic spring-mass system. A decoupling layer consisting of flexible, predominantly open-cell material is applied to this insulating layer or the heavy layer thereof, a carpet layer consisting of wear layer and underlay being attached in turn to said decoupling layer.
In addition, considerable importance is attached to the use of sound-absorbing heat shields. These are attached between vehicle components which become very hot, e.g. catalysts and/or exhaust pipes, and the vehicle floor, and reflect the heat irradiated by the catalysts and/or the exhaust pipes or insulate the floor from these hot vehicle components.
Heat shields known hitherto therefore consist substantially of a relatively thick formed sheet metal piece with a high heat reflection capacity, preferably of aluminium, to which a heat-absorbing insulating layer provided with a protective foil is applied. The insulating layer used generally consists of ceramic, rock or glass wool or foams or foil assemblies. Such heat shields are described in DE-U-87 00 919.6 or EP-0 439 432, for example.
A known heat shield with sound-absorbing effect is described in Utility Model DE-U-9107484.3, for example. This heat shield comprises a backing sheet of aluminium and includes an insulating layer consisting of a mesh of aluminium filaments. Additional layers within the insulating layer may consist of a foil perforated in the manner of expanded metal and are suitably pleated to form corrugations.
Such heat shields are currently used to reduce the noise level of vehicles. To this end, the heat shield backing sheet is at least partially perforated and the insulating assembly is of open-cell construction, in order to have a simultaneously sound-absorbing effect.
These heat shields are mounted in such a way that the absorbed heat may be dissipated by the air passing between shield and floor panel, i.e. they are spaced from the floor panel. These arrangements are self-supporting and require an extremely stable structure, in order to be able to withstand the considerable vibrations arising in vehicles. In addition, mounting of these heat shields is relatively complex. Such a heat shield is described in U.S. Pat. No. 5,464,952, for example.
The present-day automobile industry endeavours in general to produce trims which are lighter and lower in cost than existing trims while retaining at least the same technical functionality.